1. Field of the Invention
The present invention relates to an improved valve plate for use in reciprocating gas compressors of the type commonly used in vapor compression refrigeration systems and in other applications.
With the advent of the energy crisis and its attendant increases in the costs of fuel and electricity, it has become desirable and necessary that energy consuming equipment be designed to operate at the highest possible efficiencies. This is especially true in the refrigeration industry as evidenced by pending regulations of the Federal Government which would impose minimum standards on system operating efficiencies. Accordingly, the valve plate of the present invention represents an improvement in compressor design so as to attain higher operating efficiency.
Reciprocating compressors of the type under consideration may be of at least two general configurations, as dictated by the cooperative relationship between the piston crown and its associated valve plate.
In a first type, the piston crown is substantially flat and coacts with a corresponding lower planar surface of the valve plate in order to effect compression. Discharge ports pass through the valve plate in an axial direction, terminating at its upper surface where a discharge valve member is located. This particular configuration thus presents a problem for the designer in that the discharge port volume contributes to the overall clearance volume of the compressor; a factor which would favor a valve plate of minimal thickness in order to reduce compressor clearance volume and thus increase its capacity and efficiency. Working against this requirement, however, is the problem of providing adequate suction gas flow area through the valve plate, a consideration favoring a valve plate of increased overall thickness.
In a second type of reciprocating compressor, its piston includes an upstanding annular crown which cooperates with a corresponding annular discharge port formed in part by the valve plate. This type of compressor is generally of relatively high performance in that its clearance volume may be reduced to a minimum value. Although valve plate thickness is not as critical in this instance from the standpoint of reducing clearance volume, general design considerations would nonetheless favor a component of compact dimension while affording maximum suction gas flow area.
In summary, it is desirable in the design of valve plates of the type under consideration that overall thickness be minimized while providing a suction gas flow area of low resistance so as to maintain or increase compressor efficiency. Coupled with this consideration is the requirement that the valve plate be of sufficient strength to withstand the forces attendant in a reciprocating gas compressor.
2. Description of the Prior Art
It is conventional in the field of reciprocating compressors to provide a circular valve plate in overlying relationship to the cylinder bore which serves to control gas flow on the suction and discharge strokes of the piston. This is accomplished by the provision in the valve plate of radial flow paths for the suction gas extending from its periphery to suction port openings on a lower surface of the plate. Centrally located discharge port means extend through the valve plate in an axial direction. Gas flow through the valve plate is controlled by valve discs of the leaf or reed type which are disposed in overlying relationship to the ports, opening and closing in response to pressure changes in the cylinder on respective suction and discharge strokes of the compressor.
Valve plates have been proposed in the prior art which are of unitary construction, comprising a single disc-shaped element of predetermined thickness having discharge port means located in a central portion thereof, either in the form of a plurality of openings or a single circular bore to accommodate a corresponding upstanding piston crown, as described above. Suction gas flow passages are defined in such a valve plate by a plurality of radial bores extending from its periphery to an annular suction port opening located on a lower surface of the plate. This design has drawbacks in that expensive tooling is needed in order to accurately drill these radial flow passages, which further require careful deburring in order to provide proper gas flow characteristics and prevent damage to the compressor.
In order to obviate some of the manufacturing difficulties associated with the unitary design, it has been proposed that a valve plate be built-up from a plurality of laminated elements which are bonded to one another in a furnace brazing operation. Plates of this type have generally included lower and upper plate-like members in spaced relationship, with a centrally located axially extending element defining therebetween an annular suction gas flow area. Said element could either be a solid element through which a plurality of discharge port openings pass, or an annular element having a central bore to accommodate an upstanding annular piston crown. Within this annular flow area have been provided web-like or columnar elements for supporting the plate-like members at their outer peripheries. To date, these constructions have presented undesirable restrictions to suction gas flow within the valve plate itself.